Make lazy-draft default to off

Author: howard0su

dflash/src/server/http_server.h

@@ -56,7 +56,7 @@ struct ServerConfig {
     float       pflash_keep_ratio = 0.05f;  // fraction of tokens to keep
     std::string pflash_drafter_path;        // path to drafter GGUF (Qwen3-0.6B)
     bool        pflash_skip_park = false;   // skip park/unpark for ≥32GB GPUs
-    bool        lazy_draft      = true;    // park decode draft when idle to save VRAM
+    bool        lazy_draft      = false;   // park decode draft when idle to save VRAM
 
     // Disk prefix cache
     std::string disk_cache_dir;             // empty = disabled

dflash/src/server/server_main.cpp

@@ -68,7 +68,7 @@ static void print_usage(const char * prog) {
         "  --prefill-keep-ratio <F>    Fraction of tokens to keep (default: 0.05)\n"
         "  --prefill-drafter <path>    Drafter GGUF for compression (Qwen3-0.6B)\n"
         "  --prefill-skip-park         Skip park/unpark (for >=32GB GPUs)\n"
-        "  --no-lazy-draft             Keep decode draft loaded at all times\n"
+        "  --lazy-draft                Park decode draft when idle to save VRAM\n"
         "\n"
         "Disk KV cache:\n"
         "  --kv-cache-dir <path>       Directory for ondisk KV cache (enables feature)\n"
@@ -141,8 +141,8 @@ int main(int argc, char ** argv) {
             sconfig.pflash_drafter_path = argv[++i];
         } else if (std::strcmp(argv[i], "--prefill-skip-park") == 0) {
             sconfig.pflash_skip_park = true;
-        } else if (std::strcmp(argv[i], "--no-lazy-draft") == 0) {
-            sconfig.lazy_draft = false;
+        } else if (std::strcmp(argv[i], "--lazy-draft") == 0) {
+            sconfig.lazy_draft = true;
         } else if (std::strcmp(argv[i], "--kv-cache-dir") == 0 && i + 1 < argc) {
             sconfig.disk_cache_dir = argv[++i];
         } else if (std::strcmp(argv[i], "--kv-cache-budget") == 0 && i + 1 < argc) {
@@ -197,6 +197,12 @@ int main(int argc, char ** argv) {
         setenv("DFLASH27B_FA_WINDOW", "0", 0);
     }
 
+    // Lazy-draft requires both prefill-drafter AND decode draft to be useful.
+    if (sconfig.lazy_draft && !(pflash_enabled && bargs.draft_path)) {
+        std::fprintf(stderr, "[server] --lazy-draft ignored: requires both --prefill-drafter and --draft\n");
+        sconfig.lazy_draft = false;
+    }
+
     // Load tokenizer.
     std::fprintf(stderr, "[server] loading tokenizer from %s\n", bargs.model_path);
     Tokenizer tokenizer;